有人可以解释一下这段代码吗？ 它是什么意思（无符号字符）c？ 和 ft_strlen((char *)s)？

Question

在声明一些变量时，括号是什么意思。 带括号的 * 和 & 符号在这里也会造成混淆。 请解释这段代码。

#include "libft.h"    
char    *ft_strrchr(const char *s, int c)
{
    int     len;
    char    ch;

    ch = (unsigned char)c;
    len = ft_strlen((char *)s);
    if (ch == '\0')
        return ((char *)(&s[len]));
    while (--len >= 0)
    {
        if (s[len] == ch)
            return ((char *)(&s[len]));
    }
    return (NULL);
}

Answer 1

括号(type)variable将变量转换为不同的类型。

&就在变量获取该变量的 memory 地址之前。

因此，例如：

int x = 1;

char *ptr = (char *)&x; // gets the address and because it is int *, we cast it to char *
/* the above is significant, because usually int is 4 bytes and char is 1 byte, so
 * incrementing a pointer, we can go to the next byte's address if we are using a 1 byte type
 * or, it jumps 4 bytes if we are usinig int pointer. This is a reason why this is sometimes used
 * on memcpy, so that memcpy can copy all bytes to the destination
 */